Patch "ALSA: usb-audio: Properly refcounting clock rate" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ALSA: usb-audio: Properly refcounting clock rate

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-usb-audio-properly-refcounting-clock-rate.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit dc04dbbb44380b1d0bbb4b7fdc37377bd6bc131a
Author: Takashi Iwai <tiwai@xxxxxxx>
Date:   Tue Sep 20 20:11:26 2022 +0200

    ALSA: usb-audio: Properly refcounting clock rate
    
    [ Upstream commit 9a737e7f8b371e97eb649904276407cee2c9cf30 ]
    
    We fixed the bug introduced by the patch for managing the shared
    clocks at the commit 809f44a0cc5a ("ALSA: usb-audio: Clear fixed clock
    rate at closing EP"), but it was merely a workaround.  By this change,
    the clock reference rate is cleared at each EP close, hence the still
    remaining EP may need a re-setup of rate unnecessarily.
    
    This patch introduces the proper refcounting for the clock reference
    object so that the clock setup is done only when needed.
    
    Fixes: 809f44a0cc5a ("ALSA: usb-audio: Clear fixed clock rate at closing EP")
    Fixes: c11117b634f4 ("ALSA: usb-audio: Refcount multiple accesses on the single clock")
    Link: https://lore.kernel.org/r/20220920181126.4912-1-tiwai@xxxxxxx
    Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
    Stable-dep-of: 7822baa844a8 ("ALSA: usb-audio: add quirk for RODE NT-USB+")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 32a9e016665c8..2d3f814d067b5 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -39,6 +39,7 @@ struct snd_usb_iface_ref {
 struct snd_usb_clock_ref {
 	unsigned char clock;
 	atomic_t locked;
+	int opened;
 	int rate;
 	bool need_setup;
 	struct list_head list;
@@ -810,6 +811,7 @@ snd_usb_endpoint_open(struct snd_usb_audio *chip,
 				ep = NULL;
 				goto unlock;
 			}
+			ep->clock_ref->opened++;
 		}
 
 		ep->cur_audiofmt = fp;
@@ -934,8 +936,10 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
 		endpoint_set_interface(chip, ep, false);
 
 	if (!--ep->opened) {
-		if (ep->clock_ref && !atomic_read(&ep->clock_ref->locked))
-			ep->clock_ref->rate = 0;
+		if (ep->clock_ref) {
+			if (!--ep->clock_ref->opened)
+				ep->clock_ref->rate = 0;
+		}
 		ep->iface = 0;
 		ep->altsetting = 0;
 		ep->cur_audiofmt = NULL;
@@ -1656,8 +1660,7 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, bool keep_pending)
 			WRITE_ONCE(ep->sync_source->sync_sink, NULL);
 		stop_urbs(ep, false, keep_pending);
 		if (ep->clock_ref)
-			if (!atomic_dec_return(&ep->clock_ref->locked))
-				ep->clock_ref->rate = 0;
+			atomic_dec(&ep->clock_ref->locked);
 	}
 }